Coyote Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Coyote Observatory clear sky chart from 2005-11-05 to 2019-07-16.

This page is a summary of past forecasts. Even though it's based only on forecasts, some people use these pages as clue to a site's climate. But climate data based on actual observation should be preferred (if you can find it!).

Cloud, Transparency and Seeing forecasts are summarized individually. But because good observing conditions require a combination of minimum cloud cover, transparency and seeing, the individual forecast summaries can be difficult to interpret. The observing conditions section counts the combinations of conditions needed for common types of astronomical observation.

Observing Conditions

The following tables count the occurrence of the combinations of forecast and darkness conditions needed for different observations. Conditions are rated by by what percentage of the hours the observation would likely be attempted are usable.
Observation TypeMinimum conditions for hour to be usableOut of hours
Clear of CloudsTransparencySeeingSky Brightness
Planetary:50%(no limit)Average(no limit)Nighttime Hours
Deep Sky:70%Average(no limit)5.9Nighttime Hours
CCD Imaging:70%Below AveragePoor(no limit)Nighttime Hours

Percentages are of nighttime hours per month, or per year, when a particular observing conditions was met. Deep Sky percentages never exceed 50% because the moon is up half the time. Deep sky percentages are much lower for charts at high latitudes because of fewer dark hours in the summer.

Overall

PlanetaryData
Pts
Deep Sky
Max 60%
Data
Pts
Both Planetary and Deep Sky
Max 60%
Data
Pts
Either Planetary or Deep SkyData
Pts
CCD ImagingData
Pts
Night
29%
16931
13%
54194
8%
16901
35%
16901
16%
38684

By Month

MonthDays of MonthPlanetaryData
Pts
Deep Sky
Max 60%
Data
Pts
Both Planetary and Deep Sky
Max 60%
Data
Pts
Either Planetary or Deep SkyData
Pts
CCD ImagingData
Pts
January1st to 15thNight
15%
840
7%
2926
3%
836
21%
836
7%
2354
January16th to endNight
17%
896
11%
3055
5%
896
25%
896
10%
2311
February1st to 15thNight
15%
822
10%
2677
3%
821
24%
821
11%
2047
February16th to endNight
21%
735
12%
2291
5%
735
31%
735
13%
1688
March1st to 15thNight
18%
840
12%
2422
6%
840
25%
840
14%
1844
March16th to endNight
30%
896
21%
2393
9%
896
38%
896
22%
1634
April1st to 15thNight
21%
838
15%
2096
5%
838
26%
838
18%
1552
April16th to endNight
30%
741
16%
1987
7%
741
36%
741
21%
1420
May1st to 15thNight
32%
420
18%
1680
16%
420
42%
420
17%
1101
May16th to endNight
33%
439
14%
1753
10%
438
47%
438
20%
1082
June1st to 15thNight
35%
420
10%
1680
11%
420
44%
420
15%
1113
June16th to endNight
43%
420
9%
1680
11%
420
49%
420
19%
1056
July1st to 15thNight
53%
400
17%
1600
23%
400
60%
400
28%
865
July16th to endNight
56%
410
14%
1554
16%
388
61%
388
26%
897
August1st to 15thNight
52%
500
15%
1641
12%
498
56%
498
24%
1052
August16th to endNight
53%
749
21%
1991
11%
749
57%
749
35%
1242
September1st to 15thNight
46%
780
17%
1950
9%
780
48%
780
29%
1337
September16th to endNight
46%
777
22%
2129
15%
777
51%
777
31%
1367
October1st to 15thNight
31%
780
16%
2340
10%
780
39%
780
18%
1642
October16th to endNight
23%
832
11%
2578
5%
832
31%
832
12%
1939
November1st to 15thNight
26%
820
16%
2755
11%
820
33%
820
15%
1979
November16th to endNight
19%
840
9%
2940
6%
840
25%
840
9%
2287
December1st to 15thNight
17%
840
7%
2940
3%
840
22%
840
8%
2371
December16th to endNight
14%
896
9%
3136
4%
896
22%
896
8%
2504

Individual Forecasts

The length of each colored bar in the "occurrence of each Forecast" column is proportional to the number of times the chart forecast that color. The percentages are of the total number of hours per month, or per year, with a particular forecast. The colors as the same as those used in clear sky charts.

Note: Transparency probabilities are only counted for those hours that have 30% or less cloud cover. Seeing probabilities are only counted for those hours that have 80% or less cloud cover. If that's too tricky, try Observing Conditions instead.

Overall

Occurrence of each ForecastData
Points
Cloud CoverDay
17%9%36%6%34446%32%
55128
Night
16%9%46%6%34445%32%
54364
Cloud CoverDay
27%7%25%423345%32%
55138
Night
25%8%35%5%2333433%
54369
TransparencyDay
51%6%11%18%10%1
54816
Night
52%6%11%19%9%
54194
SeeingDay
23%14%30%19%9%3
7688
Night
22%12%29%24%9%
16933

By Month

Percentage Cloud Cover NE (2006-)
Color Meanings:
Overcast 90% covered 80% covered 70% covered 60% covered 50% covered 40% covered 30% covered 20% covered 10% covered Clear
MonthDays in MonthOccurrence of each ForecastData
Points
January1st to 15thDay
18%14%5%9%8%3444422%
1672
16th to endDay
13%14%5%10%8%35%445%22%
1873
February1st to 15thDay
13%14%6%12%8%35%42423%
1845
16th to endDay
18%13%47%6%45%44425%
1752
March1st to 15thDay
17%13%5%8%6%4433426%
2185
16th to endDay
14%9%45%5%33445%40%
2534
April1st to 15thDay
22%11%36%5%23435%31%
2512
16th to endDay
22%8%26%424345%36%
2591
May1st to 15thDay
21%8%36%5%24345%34%
2931
16th to endDay
16%6%36%5%345%47%35%
3066
June1st to 15thDay
21%7%35%5%34446%32%
2940
16th to endDay
17%6%25%5%35%5%6%7%34%
2940
July1st to 15thDay
10%5%24436%5%7%8%41%
2940
16th to endDay
12%425%6%35%6%7%9%35%
2882
August1st to 15thDay
11%6%27%6%36%5%6%7%36%
2560
16th to endDay
12%5%25%5%35%5%6%7%39%
2549
September1st to 15thDay
16%5%245%24448%40%
2340
16th to endDay
14%42443345%6%45%
2158
October1st to 15thDay
21%8%36%5%34446%31%
1950
16th to endDay
25%9%36%6%4443426%
1996
November1st to 15thDay
17%10%36%5%345%45%32%
1760
16th to endDay
21%12%5%7%6%45%445%22%
1680
December1st to 15thDay
19%16%5%10%7%45%445%16%
1680
16th to endDay
20%15%6%9%6%23435%21%
1792
January1st to 15thNight
16%14%6%10%8%35%5%4418%
2926
16th to endNight
13%15%5%9%8%25%445%25%
3055
February1st to 15thNight
13%15%6%10%7%35%346%24%
2675
16th to endNight
15%10%47%7%3445%6%28%
2291
March1st to 15thNight
17%13%6%8%6%3333428%
2410
16th to endNight
14%7%45%5%33445%40%
2393
April1st to 15thNight
22%7%36%433345%33%
2096
16th to endNight
21%8%25%5%23345%36%
1987
May1st to 15thNight
20%8%25%42334438%
1680
16th to endNight
14%5%245%2445%7%40%
1751
June1st to 15thNight
17%6%36%4345%46%36%
1680
16th to endNight
14%6%25%435%5%6%7%39%
1680
July1st to 15thNight
9%434425%5%48%49%
1680
16th to endNight
9%424435%47%8%45%
1650
August1st to 15thNight
8%5%25%6%345%6%8%42%
1651
16th to endNight
9%425%4245%47%50%
1991
September1st to 15thNight
15%5%25%5%33446%43%
1950
16th to endNight
15%5%24423245%48%
2129
October1st to 15thNight
20%7%25%5%3445%6%34%
2340
16th to endNight
22%11%36%5%25%445%28%
2578
November1st to 15thNight
20%9%36%6%24346%31%
2755
16th to endNight
22%13%5%8%6%24345%23%
2940
December1st to 15thNight
19%16%5%8%6%35%44420%
2940
16th to endNight
21%14%6%8%7%3434421%
3136

Percentage Cloud Cover SE (2006-)
Color Meanings:
Overcast 90% covered 80% covered 70% covered 60% covered 50% covered 40% covered 30% covered 20% covered 10% covered Clear
MonthDays in MonthOccurrence of each ForecastData
Points
January1st to 15thDay
19%14%5%8%6%3344424%
1672
16th to endDay
15%14%5%9%8%35%445%24%
1873
February1st to 15thDay
19%13%5%11%6%2442425%
1845
16th to endDay
23%12%46%7%35%34325%
1752
March1st to 15thDay
38%8%25%42322326%
2196
16th to endDay
36%5%2331223334%
2533
April1st to 15thDay
31%8%3431332332%
2512
16th to endDay
31%6%2431233435%
2591
May1st to 15thDay
38%6%2431223330%
2931
16th to endDay
34%41432333433%
3066
June1st to 15thDay
31%5%24424335%31%
2940
16th to endDay
29%414424346%33%
2940
July1st to 15thDay
11%424435%5%6%9%42%
2940
16th to endDay
12%425%5%346%7%9%38%
2882
August1st to 15thDay
36%314434345%26%
2560
16th to endDay
37%313323336%31%
2549
September1st to 15thDay
20%424424347%41%
2340
16th to endDay
18%424323445%44%
2158
October1st to 15thDay
24%7%35%434446%32%
1950
16th to endDay
26%8%36%5%3433429%
1996
November1st to 15thDay
26%8%2432342436%
1760
16th to endDay
27%10%45%5%3423327%
1680
December1st to 15thDay
23%14%5%8%7%34435%19%
1680
16th to endDay
24%14%5%7%5%2344423%
1792
January1st to 15thNight
20%13%5%8%7%35%44323%
2926
16th to endNight
16%14%5%8%6%2443428%
3055
February1st to 15thNight
20%14%5%8%6%23345%26%
2668
16th to endNight
23%9%37%6%24445%29%
2291
March1st to 15thNight
38%8%35%41222326%
2422
16th to endNight
36%42432222335%
2393
April1st to 15thNight
29%5%25%41222437%
2096
16th to endNight
25%6%2432233439%
1987
May1st to 15thNight
33%5%1332223337%
1680
16th to endNight
27%5%13313335%40%
1751
June1st to 15thNight
22%5%25%423445%39%
1680
16th to endNight
19%41443445%5%41%
1680
July1st to 15thNight
9%32441445%7%50%
1680
16th to endNight
10%41443447%8%46%
1650
August1st to 15thNight
31%313423345%34%
1651
16th to endNight
32%21331223440%
1991
September1st to 15thNight
18%414424346%44%
1950
16th to endNight
19%414422235%49%
2129
October1st to 15thNight
23%6%25%423345%36%
2340
16th to endNight
25%8%36%424345%31%
2578
November1st to 15thNight
32%7%2442222333%
2755
16th to endNight
34%10%36%41223327%
2940
December1st to 15thNight
25%13%46%5%3344424%
2940
16th to endNight
28%12%38%6%3333323%
3136

Transparency (when cloud cover <= 30%)
Color Meanings:
Too cloudy to forecast Poor Below Average Average Above average Transparent
MonthDays in MonthOccurrence of each ForecastData
Points
January1st to 15thDay
64%5%9%12%6%1
1673
16th to endDay
63%5%10%12%6%
1873
February1st to 15thDay
63%410%15%4
1847
16th to endDay
60%5%10%13%9%1
1752
March1st to 15thDay
61%5%10%15%6%
2196
16th to endDay
45%48%19%15%5%
2534
April1st to 15thDay
55%47%16%13%2
2512
16th to endDay
50%47%17%15%3
2591
May1st to 15thDay
51%5%8%18%14%1
2931
16th to endDay
46%7%12%19%11%1
3070
June1st to 15thDay
52%6%9%19%10%1
2940
16th to endDay
46%8%11%20%11%1
2940
July1st to 15thDay
34%7%14%26%15%1
2791
16th to endDay
41%9%16%22%9%
2715
August1st to 15thDay
44%9%15%20%9%
2546
16th to endDay
39%8%15%25%9%
2549
September1st to 15thDay
41%6%13%25%12%
2340
16th to endDay
38%7%13%29%10%
2158
October1st to 15thDay
52%6%11%19%8%
1950
16th to endDay
60%6%12%14%4
1996
November1st to 15thDay
51%7%14%18%7%
1760
16th to endDay
63%6%10%11%6%1
1680
December1st to 15thDay
68%7%11%9%3
1680
16th to endDay
64%6%10%11%5%
1792
January1st to 15thNight
67%5%9%11%4
2926
16th to endNight
60%5%9%16%7%
3055
February1st to 15thNight
61%5%12%16%4
2677
16th to endNight
55%6%11%18%8%
2291
March1st to 15thNight
59%411%17%7%
2422
16th to endNight
45%49%20%16%3
2393
April1st to 15thNight
52%48%18%14%1
2096
16th to endNight
49%47%17%17%2
1987
May1st to 15thNight
47%5%8%19%15%3
1680
16th to endNight
41%7%13%20%15%2
1753
June1st to 15thNight
47%7%11%19%11%1
1680
16th to endNight
41%8%13%21%14%
1680
July1st to 15thNight
30%7%13%27%18%1
1600
16th to endNight
34%8%16%25%15%
1554
August1st to 15thNight
37%10%16%23%11%
1641
16th to endNight
32%6%16%31%12%
1991
September1st to 15thNight
40%7%12%27%11%1
1950
16th to endNight
38%5%12%34%9%
2129
October1st to 15thNight
48%6%10%21%12%
2340
16th to endNight
56%6%14%15%6%
2578
November1st to 15thNight
53%6%12%17%9%
2755
16th to endNight
62%6%11%15%3
2940
December1st to 15thNight
65%6%12%11%3
2940
16th to endNight
66%5%10%11%5%
3136

Seeing (when cloud cover <= 80%)
Color Meanings:
Too cloudy to forecast Bad 1/5 Poor 2/5 Average 3/5 Good 4/5 Excellent 5/5
MonthDays in MonthOccurrence of each ForecastData
Points
January1st to 15thDay
25%23%29%15%5%
120
16th to endDay
29%18%41%9%
151
February1st to 15thDay
35%24%33%6%
180
16th to endDay
33%23%27%12%2
255
March1st to 15thDay
29%17%33%16%3
390
16th to endDay
24%18%30%18%7%1
416
April1st to 15thDay
31%21%28%12%5%
390
16th to endDay
28%18%25%15%10%2
379
May1st to 15thDay
31%14%27%16%7%2
408
16th to endDay
22%15%35%17%6%1
459
June1st to 15thDay
28%8%32%20%8%1
435
16th to endDay
17%12%34%23%10%
435
July1st to 15thDay
12%431%30%16%4
425
16th to endDay
12%5%30%31%15%4
391
August1st to 15thDay
13%6%27%32%12%7%
358
16th to endDay
14%6%25%27%15%9%
396
September1st to 15thDay
17%6%28%17%18%11%
375
16th to endDay
14%12%27%18%16%9%
374
October1st to 15thDay
24%12%29%22%8%2
375
16th to endDay
29%20%27%16%4
374
November1st to 15thDay
30%14%27%20%6%1
234
16th to endDay
35%22%31%8%2
120
December1st to 15thDay
24%20%36%17%1
120
16th to endDay
34%22%28%11%3
128
January1st to 15thNight
25%18%34%17%4
840
16th to endNight
22%17%35%20%3
896
February1st to 15thNight
21%16%38%19%3
824
16th to endNight
21%19%33%21%4
735
March1st to 15thNight
25%15%33%20%4
840
16th to endNight
19%15%30%24%9%
896
April1st to 15thNight
27%16%29%20%5%
838
16th to endNight
27%13%25%23%9%
741
May1st to 15thNight
26%8%26%27%9%1
420
16th to endNight
16%7%37%26%11%
439
June1st to 15thNight
20%7%29%32%9%
420
16th to endNight
16%6%28%35%12%
420
July1st to 15thNight
8%426%43%16%1
400
16th to endNight
10%126%45%14%1
410
August1st to 15thNight
11%423%38%20%1
500
16th to endNight
11%424%35%20%2
749
September1st to 15thNight
17%5%25%28%20%2
780
16th to endNight
17%9%23%24%22%3
777
October1st to 15thNight
24%10%29%22%11%1
780
16th to endNight
28%15%27%22%6%
832
November1st to 15thNight
26%12%29%21%9%
820
16th to endNight
32%17%24%18%6%
840
December1st to 15thNight
27%17%32%18%3
840
16th to endNight
31%14%31%18%3
896
Page generated at 2019-07-17 08:53:06. Version ac04

Copyright 2019 A. Danko


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